I did overstate the velocity of 30-06 - 220 grain. 2,300 - 2,400 IS more like it. I only used a quickie example without trying to be explicit. I prefer the .338 Winchester Magnum over the 30-06.

When I suggested loads for the shotgun I was referring to the big pellets/shot not bird shot. Here's a chart with size, velocity and pellet count.

http://www.unluckyhunter.com/2011/07/choosing-best-buckshot-part-1.html

Pretty impressive velocities. Up over handgun velocities. 1,400 - 1,600 fps! 15 to 50 pellets. One shot is like hitting him all at once with a couple of dozen .22 handguns.

I shot lots of shotguns in my day. And patterned them. The shot spreads out rather quickly depending on the choke. A rib and bead are plenty good at 20 yards.

My grandson presently works at a trap and skeet range 5 days a week during summer vacation from college. He's really good.

Compared to trap and skeet or wild turkey, pheasant, grouse, quail, ducks, dusting a bear up close with buck shot is very, very do-able with great success under the right circumstances. Of course, if he blind sides you or attacks from then rear that could be a big problem. In that case have the handgun available as a side arm.